Lens exposure during brain scans using multidetector row CT scanners: methods for estimation of lens dose.

BACKGROUND AND PURPOSE: Some recent studies on radiation lens injuries have indicated much lower dose thresholds than specified by the current radiation protection guidelines. The purpose of this research was to measure the lens dose during brain CT scans with multidetector row CT and to assess methods for estimating the lens dose. MATERIALS AND METHODS: With 8 types of multidetector row CT scanners, both axial and helical scans were obtained for the head part of a human-shaped phantom by using normal clinical settings with the orbitomeatal line as the baseline. We measured the doses on both eyelids by using an RPLGD during whole-brain scans including the orbit with the starting point at the level of the inferior orbital rim. To assess the effect of the starting points on the lens doses, we measured the lens doses by using 2 other starting points for scanning (the orbitomeatal line and the superior orbital rim). RESULTS: The CTDIvols and the lens doses during whole-brain CT including the orbit were 50.9-113.3 mGy and 42.6-103.5 mGy, respectively. The ratios of lens dose to CTDIvol were 80.6%-103.4%. The lens doses decreased as the starting points were set more superiorly. The lens doses during scans from the superior orbital rim were 11.8%-20.9% of the doses during the scans from the inferior orbital rim. CONCLUSIONS: CTDIvol can be used to estimate the lens dose during whole-brain CT when the orbit is included in the scanning range.

Vascular anatomy of the pancreas and clinical applications.

The development of recent technology, especially the helical computed tomography (CT) scan, allows us to observe small peripancreatic vessels which previously could be demonstrated only by angiography (1), and therefore make three-dimensional (3-D) volume rendered CT angiographic reconstruction possible (2). The neighboring structures as well as the pancreatic vessels are clearly visualized on the axial CT scan. Therefore, it is necessary to define the peripancreatic vessels on the axial images, as well as on angiography to make an accurate diagnosis of pancreatic disease so that we can also estimate the dynamic flow of the peripancreatic vessels. In this chapter, I would like to use the cadaver dissections of pancreatic vessels to explain each pancreatic vessel based on previous anatomic and radiologic references and finally demonstrate the clinical cases in terms of the pancreatic vessels. The pancreatic arteries and veins are explained based on the anatomic and radiologic references. Principal pancreatic vessels are demonstrated on cadaver dissection. The pancreas head is supplied by the anterior and posterior pancreaticoduodenal arteries forming arcades in the pancreaticoduodenal sulcus and is drained by the pancreaticoduodenal veins. The pancreas body and tail are supplied by the dorsal, inferior, and caudate pancreatic arteries, and are drained by the inferior and left pancreatic veins. Clinical applications in terms of the pancreatic vessels such as basis for interpretation of the angiography and the CT scan, treatment of pancreatitis and pancreatic cancer, detection of small insulinoma are stated.

The subclavius posticus muscle: a factor in arterial, venous or brachial plexus compression?

During dissection practice in 1993 and 1995 to 1999, we found an aberrant muscle which connected the first costal cartilage and the superior margin of the scapula in 12 sides (4.8%) of 11 cadavers (8.9%) among 248 sides of 124 cadavers. The muscle originated from the cranial surface of the sternal end of the first rib, ran laterodorsally, and inserted into the superior margin of the scapula. According to the origin and insertion, the aberrant muscle was considered to be the subclavius posticus (Rosenmüller, 1800). We also examined the supraclavicular region of a living subject by MR imaging to estimate the course of such an aberrant muscle. It is thought that the aberrant muscle runs on the anterior surface of the subclavian vein and crosses over the brachial plexus. Such a muscle could be considered as a possible factor causing the Paget-von Schrötter syndrome which is recognized as spontaneous or effort-related thrombosis of the axillo-subclavian vein. It is recommended to take into account the possible existence of such an aberrant muscle during the examination of patients with thoracic outlet syndrome, especially in those with symptoms of venous compression.

The congenital anastomoses between hepatic arteries: angiographic appearance.

The purpose of this study was to evaluate congenital anastomoses between hepatic arteries demonstrated on angiography in ten patients and to correlate the anastomosis with types of hepatic arterial anatomy. We evaluated the types of the hepatic arterial anatomy based on Michels' classification for 720 patients and compared the anatomic types between the patients with the anastomoses (ten patients) and without the anastomoses (710 patients). The diameter of the anastomoses ranged from 1.5 to 3.0 mm (mean, 2.4 mm). Five anastomoses were classified as tortuous type and five as straight type. Based on Michels' classification for types of hepatic arterial anatomy, eight (80%) of ten patients with the congenital anastomoses were classified as type III (replaced right hepatic artery from superior mesenteric artery). The remaining two patients were classified as type IV (replaced right hepatic artery from superior mesenteric artery and replaced left hepatic artery from left gastric artery) and type VIIIa (replaced right hepatic artery from superior mesenteric artery and accessory left hepatic artery from left gastric artery). Eight (16%) of 48 patients who were classified as type III have the anastomoses. In conclusion, the congenital anastomoses were observed especially in patients with replaced right hepatic artery from superior mesenteric artery.

Balloon-occluded retrograde transvenous obliteration of gastric varix draining via the left inferior phrenic vein into the left hepatic vein.

We encountered a patient with gastric varix draining not via the usual left suprarenal vein but via the left inferior phrenic vein joining the left hepatic vein. Transfemoral balloon-occluded retrograde transvenous obliteration (BRTO) of the varix was performed under balloon occlusion of the left inferior phrenic vein via the left hepatic vein and retrograde injection of the sclerosing agent (5% of ethanolamine oleate) into the gastric varix. Disappearance of the gastric varix was confirmed on endoscopic examination 2 months later.

Precaval draining vein from paraesophageal varices: radiologic-anatomic correlation.

OBJECTIVE: The purpose of this study was to describe the CT features of the precaval draining vein from paraesophageal varices in six patients with liver cirrhosis. We also assessed the anatomic nature of the vein. CONCLUSION: The precaval vein courses anteriorly to the inferior vena cava and drains into the right anterior aspect of the inferior vena cava. The diameter of the precaval vein ranged from 3 to 13 mm (mean, 6.5 mm). The precaval vein is anatomically identical to the anastomosis between the right and left inferior phrenic veins.

Veins of Retzius at CT during arterial portography: anatomy and clinical importance.

PURPOSE: To classify the veins of Retzius demonstrated at computed tomography (CT) during arterial portography (CTAP) on the basis of anatomic location and to evaluate the relationship between the frequency of CT visualization and associated disease. MATERIALS AND METHODS: The authors reviewed axial CTAP scans from 130 patients. Patients were classified into one of two groups: patients with liver cirrhosis (group 1 [n = 81]) and patients without liver cirrhosis (group 2 [n = 49]). RESULTS: The pathways of the veins of Retzius were classified as follows: (a) The ileocolic vein drained into the inferior vena cava (IVC) or the right renal vein through the right gonadal vein (n = 61); (b) the pancreaticoduodenal vein drained into the IVC (n = 8); (c) the proximal branches of the superior mesenteric vein drained into the left gonadal vein (n = 6); and (d) the ileocolic vein drained directly into the IVC (n = 5). The veins of Retzius were demonstrated in 41 (51%) of the 81 patients in group 1 and 26 (53%) of the 49 patients in group 2. There was no statistically significant difference between the two groups. CONCLUSION: The veins of Retzius were demonstrated at CTAP in approximately 50% of patients with and 50% of patients without liver cirrhosis.

Preaortic esophageal veins: CT appearance.

OBJECTIVE: The purpose of this study was to describe the CT imaging features of preaortic esophageal veins in 10 patients with liver cirrhosis. CONCLUSION: Preaortic esophageal veins deriving from the paraesophageal varices course anterior to the descending aorta and drain into the hemiazygos vein. Preaortic esophageal veins are anatomically identical to extrinsic esophageal veins. The diameter of the veins we studied ranged from 1 to 8 mm (mean, 3.1 mm). Two preaortic esophageal veins were noted in each of two patients.

Hepatic falciform ligament artery: angiographic anatomy and clinical importance.

The hepatic falciform ligament artery (HFLA) was evaluated by angiography and also by dissections. Based on the findings, the mechanism of the post-chemoembolization skin rash was studied. A total of 340 liver cirrhosis patients who underwent hepatic artery chemoembolization for hepatocellular carcinoma were reviewed in terms of the angiographic incidence of the HFLA, variations in its origin, and the incidence of skin rash. The HFLA was demonstrated in 26 (7.6%) of the 340 patients on angiography. Two HFLAs were observed in one patient. The origin was the middle hepatic artery (A4) in 16 cases, the superior branch of the middle hepatic artery in three, the inferior branch of the middle hepatic artery in two, the inferior branch of the left hepatic artery (A3) in three, and the confluence of A3 and A4 in three cases. There were no patients who developed post-chemoembolization skin rash. Two cadavers were dissected to investigate the anastomosis between the HFLA and the subcutaneous artery. Two different anastomoses were found: (1) direct and (2) via the ensiform branch of the internal thoracic artery. These were located at the lower and upper part of the falciform ligament, respectively. The distribution of a chemotherapeutic agent through these anastomoses is the likely cause of post-chemoembolization skin rash. If prophylactic embolization of the proximal portion of the HFLA using a metallic coil is performed, the skin rash will be prevented.

Primary Malignant Lymphoma of the Breast: Mammographic and Ultrasonographic Findings.

Malignant lymphoma rarely involves the breast. We discribe four cases of primary breast lymphoma encountered in our institution from 1979 through 1996, focusing on mammographic and ultrasonographic findings. The lymphomas were demonstrated by mammography as a well-defined mass in one case, an ill-defined mass in two cases and as diffuse increased opacity in one case. No desmoplastic change or calcification was noted. In 3 cases ultrasonography was used, revealing hypoechoic masses with (1 case) or without (2 case) posterior enhancement. During the past two years, 45 of 197 cancers (23%) were demonstrated as a mass without desmoplastic change or calcification by mammography and ultrasonography at our institution. It can be difficult to distinguish malignant lymphoma from more common diseases of the breast, such as carcinoma, by mammography and ultrasonography.

Wedge-shaped lesion in the liver seen on postoperative CT. Probable thromboembolic phenomenon in the portal venous system.

PURPOSE: To demonstrate CT findings of a wedge-shaped lesion (WSL) in the liver following abdominopelvic surgery and to determine the etiology and incidence of WSL. MATERIAL AND METHODS: Retrospective review of teaching files in our institution revealed 18 cases showing postoperative WSL in the liver. We also retrospectively reviewed CT images of the liver in 104 patients with a recent history of abdominopelvic surgery performed during a period of 12 months, as well as in 102 patients with no history of surgery during the same period to be used as control. Three additional patients with WSL were found in the postoperative group and none in the control group. Liver CT images from the 21 patients showing WSL, along with their clinical data and follow-up CT where available, were retrospectively analyzed. RESULTS: I.v. contrast-enhanced CT showed homogeneous higher attenuation of WSL than the surrounding liver in all cases; unenhanced CT showed low density in 5 patients, isodensity in 7 patients, and high density in 5 patients as compared with the surrounding liver. Density on unenhanced CT was significantly correlated with the presence or grade of fatty liver (p<0.01). In 5 cases CT demonstrated clots in the portal vein branch within the area of WSL and in 2 cases portal perfusion defects were observed on arterial portal CT, corresponding to the areas of WSL. Follow-up CT examinations were available on 15 patients: WSL became less prominent, or atrophic, or showed no change in 10, 2 and 3 patients respectively. Follow-up CT showed development of liver metastasis in only 3 cases. Only 2 of the 21 patients were clinically symptomatic; one had postoperative ileus and the other obstructive jaundice. CONCLUSION: Postoperative WSL may represent a thromboembolic phenomenon at the peripheral intrahepatic branch of the portal venous system during or after abdominopelvic surgery, resulting in a compensatory increase in the hepatic arterial flow that appears as wedge-shaped enhancement on CT. This is a clinically asymptomatic and uncommon phenomenon (occurring in 3% of abdominopelvic surgeries). It is important that this phenomenon is not confused with liver metastasis.

Peripancreatic veins on thin-section (3 mm) helical CT.

OBJECTIVE: The purpose of this study was to evaluate thin-section helical CT for the frequency of visualization of the peripancreatic veins, the venous anatomy at the head of the pancreas, and variations of the venous anatomy. SUBJECTS AND METHODS: We performed 30-sec helical CT of the pancreas with one breath-hold and a 3-mm scanning collimation in 50 patients. The scan was started 60 sec after injection of an i.v. contrast medium at the rate of 2 ml/sec (total amount of contrast medium, 100 ml). The axial scan data were reviewed for the following information: the frequency of CT visualization of the peripancreatic veins (anterior superior pancreaticoduodenal vein, first jejunal vein, gastrocolic trunk, inferior mesenteric vein, left gastric vein, middle colic vein, posterior superior pancreaticoduodenal vein, right colic vein, and right gastroepipolic vein) and the anatomic relationship between the large portal venous system (portal vein, superior mesenteric vein, and splenic vein) and its tributaries. RESULTS: The frequency of visualization on CT of each vessel was gastrocolic trunk, 100%; right gastroepiploic vein, 100%; first jejunal vein, 96%; inferior mesenteric vein, 88%; left gastric vein, 80%; posterior superior pancreaticoduodenal vein, 72%; middle colic vein, 72%; right colic vein, 64%; and anterior superior pancreaticoduodenal vein, 50%. The anatomic relationship between the large portal venous system and its tributaries was as follows: The left gastric vein drained into the splenic vein-portal vein confluence (46%), into the splenic vein (32%), and into the portal vein (22%); the inferior mesenteric vein drained into the splenic vein (46%), the splenic vein-superior mesenteric vein confluence (25%), and the superior mesenteric vein (29%). The posterior superior pancreaticoduodenal vein drained into the portal vein above the splenic vein-portal vein confluence (mean distance, 0.3 cm). The middle colic vein, gastrocolic trunk, and first jejunal vein drained into the superior mesenteric vein below the splenic vein-portal vein confluence (mean distances of 2.4 cm, 3.0 cm, and 3.7 cm, respectively). CONCLUSION: Thin-section helical CT scans provide good visualization of the peripancreatic veins.

Helical CT angiography with multiplanar reformation: techniques and clinical applications.

The technique and potential clinical applications of multiplanar reformation (MPR) of imaging data from helical computed tomography (CT) to display images of the blood vessels in the abdomen and the thorax are described. Helical CT was performed following bolus intravenous contrast material enhancement in patients with suspected tumor involvement of vessels in various regions of the body. The axial images were stacked to form a volume of imaging data from which a plane could be selected to display the desired vascular image in a two-dimensional format. Various techniques were used to change the image plane so that different vessels in different regions of the body could be displayed, including the splanchnic vessels around the pancreas, the portal veins and hepatic artery in the porta hepatis, the renal vessels, and the venae cavae and aorta. Rotation from a coronal or sagittal plane was necessary to display most vessels. The technique is practical and reproducible, but it requires that the operator be knowledgeable about vascular anatomy. Helical CT angiography with MPR has the potential to display vascular images that are similar to angiograms.

Repeat embolization of the side branch of the internal mammary artery graft by gelatin sponge particles and micro coils.

The internal mammary artery (IMA) is increasingly used as a coronary bypass conduit because of better long-term patency and improved prognosis as compared with venous grafts. Previous investigators have suggested that the "steal" of blood flow of the IMA graft via the subclavian artery or a persistent large side branch of the graft may lead to its thinning. However, only a few reports have described the embolization of a large side branch using a transcatheter procedure. We present a case of repeated embolization of a large lateral costal side branch of the left internal mammary arterial graft applying gelatin sponge particles and micro coils, as well as angioplasty to the graft conduit, with resulting easing of chest pain.

Embolization with steel coils using a saline flush technique.

A method using saline flush to push Gianturco steel coils through catheters is described, and has been successfully used in 45 patients. The saline flush technique requires no precise matching of coils and catheters, solves problems associated with the conventional method and simplifies the coil embolization procedure.

Hepatic inferior vena cava obstruction: treatment of two types with Gianturco expandable metallic stents.

Gianturco expandable metallic stents were used for treating six patients with inferior vena cava (IVC) obstruction due to compression by large hepatic tumors and three patients with idiopathic obstruction of the hepatic IVC and Budd-Chiari syndrome who showed reocclusion or stenosis 3-21 months after previously performed percutaneous transluminal angioplasty (PTA). In all six patients with compression by hepatic tumors, stents dilated the IVC and debilitating edema of the lower body disappeared. In the three patients with idiopathic obstruction, stents were placed after repeat dilation of the lesions and Budd-Chiari syndrome did not recur during a follow-up period of 7-10 months. In two of the three, cavograms obtained 8 months after placement showed the channels to be open with minimal intimal thickening. Gianturco expandable metallic stents can correct IVC obstruction due to compression by hepatic tumors and are useful in preventing reocclusion of the IVC after PTA for the treatment of idiopathic obstruction. The authors recommend using tanem stents connected by at least two struts.

[Lipiodol-CT for the detection of small hypovascular HCC].

To evaluate the diagnostic value of Lipiodol-CT for small hypovascular HCC, we injected 3 ml or less Lipiodol into the hepatic artery of patients with chronic liver disease and small SOL in the liver detected on echogram but not on angiogram. About seven days after injection CT was used to check for accumulation of Lipiodol in the liver SOL. We found that the sensitivity of this method for detection of hypovascular HCC is only 25%. We assume that Lipiodol does not accumulate in small hypovascular HCC lesions because they have little vascular stroma. Lipiodol-CT has high diagnostic value for the detection of small hypervascular daughter HCC lesions, but this method should not be relied on for the detection of small hypovascular HCC.

[Usefulness of dynamic thin section CT in detecting lymph node metastasis of lung cancer].

The diagnosis for metastatic lymph nodes of lung cancer by the conventional CT is done only by the size of nodes, therefore, its diagnostic accuracy is questionable. For the purpose of more qualitative diagnosis in order to elevate accuracy of metastatic nodes, we studied a new CT image (Dynamic Thin Section CT) by combining the Thin Section CT with the Dynamic CT, and reviewed on the image of histopathological positive nodes. Firstly, for the preoperative cases of lung cancer, the conventional CT was performed for the whole chest with 10 mm-thickness and 10 mm-interval. Secondary, among them, the Dynamic CT by bolus-injection at the sites of detected hilar and mediastinal lymph nodes was performed. For this method, the Thin Section CT with 2 mm-thickness was used, and the image-detected nodes were isolated by surgery. We studied 25 cases whose images were compared with the histological findings. By the conventional CT sensitivity were 35.7%, specificity 54.5%, and accuracy 44.0%, in regarding the shorter diameter over 1 cm as positive nodes, then under diagnosis were 36%, over diagnosis 20%. Morphological features were reviewed on the image of metastatic lymph nodes in the Dynamic Thin Section CT, and were (1) lump-like lymph nodes, (2) disappearance of the fatty plane around the lymph nodes or uneven and irregular margins, (3) irregular internal structures of enhanced lymph nodes. Moreover, small lymph nodes were clearly detected, and the size was exactly measured.(ABSTRACT TRUNCATED AT 250 WORDS)